Catchable fatal error

-- HikaShop version -- : 2.6.2
-- Joomla version -- : 3.5.0
-- PHP version -- : 5.4.45
-- Browser(s) name and version -- : Firefox 39.0.3
-- Error-message(debug-mod must be tuned on) -- : Catchable fatal error: Object of class stdClass could not be converted to string in /home/tiffinta/public_html/administrator/components/com_hikashop/helpers/helper.php on line 2578

After making a purchase using PaypalPro, the sale goes through but we get this error message
Catchable fatal error: Object of class stdClass could not be converted to string in /home/tiffinta/public_html/administrator/components/com_hikashop/helpers/helper.php on line 2578

Help!! This is urgent!!